The present invention relates to an activating composition of metallocene complexes in the catalysis of processes for the (co)polymerization of xcex1-olefins.
More specifically, the present invention relates to an organometallic composition without boron and with a low content of other metals, particularly aluminum, capable of forming a catalyst with a high activity for the polymerization of xcex1-olefins, combined with metallocene complexes of group 4 -of the periodic table of elements. The present invention also relates to said catalyst, as well as a polymerization process of xcex1-olefins which uses it.
It is generally known in the art that ethylene, or xcex1-olefins in general, can be polymerized or copolymerized by means of low, medium or high pressure processes with catalysts based on a transition metal. A particular group of catalysts active in the polymerization of olefins consists of the combination of an organic oxyderivative of aluminum (in particular, polymeric methylaluminoxane or MAO) with an xcex75-cyclopentadienyl derivative (metallocene) of a transition metal of group 4 of the periodic table of elements (in the form approved by IUPAC and published by xe2x80x9cCRC Press Inc.xe2x80x9d in 1989). For a known preparation technique of the above compounds, reference can be made to the description of H. Sinn, W. Kaminsky, in Adv. Organomet. Chem., vol.18 (1980), page 99 and to the U.S. Pat. No. 4,542,199.
In spite of the numerous advantages with respect to the prior known art, represented by traditional heterogeneous catalysts, of the so-called Ziegler-Natta type, having a multicentric nature, catalysts based on metallocenes have also proved to have various disadvantages which have limited their industrial development. Among these the production of polymers with an insufficient average molecular weight, especially with high temperature polymerization processes, an unsatisfactory activation rapidity of the catalytic system in processes characterized by reduced residence times in the reactor, the use of significant quantities of MAO activator and the difficulty of preparing and conserving the latter on an industrial scale, can be mentioned.
In an attempt to overcome problems in particular relating to the use of MAO, metallocene-type catalysts capable of polymerizing olefins also without aluminum compounds, or in the presence of a more limited quantity of this metal, have recently been developed. These systems however are based on the formation of a catalytic species of a cationic nature, obtained by contact of a suitable metallocene with an activator consisting of a strong Lewis acid or, more advantageously, of an organometallic salt whose anion has a delocalized charge and is weakly co-ordinating, normally a fluorinated tetra-arylborane. Various cationic systems of this type are described for example, in the publications of R. R. Jordan in xe2x80x9cAdvances in Organometallic Chemistryxe2x80x9d vol. 32 (1990), pages 325-387, and X. Yang et al. in xe2x80x9cJournal of the American Chemical Societyxe2x80x9d, vol. 116 (1994), page 10015, which provide, in addition to a wide description of the field, numerous patent references on the matter.
The activity of cationic metallocene catalytic systems is however generally lower than that, which is considerable, of systems using methylalumoxane. In addition, the known methods for the preparation of the above ionic activators based on fluoroarylboranes are complex with not completely satisfactory yields, thus further limiting the industrial use of cationic catalysts. Another disadvantage lies in the sensitivity of these ionic activators to air and humidity which makes their transfer and storage difficult.
Another aspect of the above catalysts, both ionic and those based on MAO, which is not entirely satisfactory, relates to their behaviour in the copolymerization of ethylene with xcex1-olefins and/or dienes, to produce linear low density polyethylene or olefinic elastomers, again owing to the difficulty of obtaining copolymers with sufficiently high molecular weights, suitable for their multiple industrial applications. The necessity is known, in fact, of operating with high quantities of comonomer to insert the desired quantity into the copolymer, with a consequent increase in the chain transfer reaction rate, which is competitive with the polymerization, and production of unsatisfactory molecular weights. This drawback becomes even more critical when operating with high temperature polymerization processes in which the chain transfer reaction is already significant without the comonomer.
Other cationic systems based on metallocenes and fluoroaryl aluminates are described in international patent application WO 98/0715, which claims a higher catalytic activity. These catalysts however are relatively complex to prepare and are particularly unstable to air and humidity, similarly to those containing boro-anions and are not easily adaptable to non-alkylated metallocene complexes.
The Applicant has now found a new group of activators of metallocene complexes, suitable for forming (co)po-lymerization catalysts of xcex1-olefins with a high activity and without the above disadvantages. These activators are based on certain extensively fluorinated di-unsaturated cyclic compounds, and allow the preparation of high activity catalysts with a low aluminum content. In particular, they can be prepared at the moment of use starting from precursors obtained with processes analogous to known and relatively simple processes, which are stable to air and humidity, thus solving the problem of handling, transfer and storage.
A first object of the present invention therefore relates to an organometallic composition which can be used as activator of a metallocene complex of a metal of group 4 to form a (co)polymerization catalyst of xcex1-olefins, characterized in that it comprises the reaction product between:
(A) a fluorinated organic compound, comprising at least one di-unsaturated cycle with 5 or 6 carbon atoms, having the following formula (I): 
wherein: each Ri group (i being an integer from 1 to 7) is a substituent of the di-unsaturated cycle independently selected from hydrogen, fluorine and a fluorinated or non-fluorinated, aliphatic or aromatic hydrocarbyl group, having from 1 to 20 carbon atoms, optionally joined to a different Ri hydrocarbyl group to form a further cycle,
on the condition that at least two, preferably at least three, of the groups R1, R2, R3 R4 or R5 are is independently selected from the group consisting of:
fluorine, or
a fluorinated alkyl group having the formula xe2x80x94CF(R9R10), wherein each R9 or R10 group can have any of the above meanings of the Ri groups and at least one of them is fluorine, or fluorinated alkyl at least in position 1, or a fluorinated aryl ArF as defined below, or a fluorinated vinyl group VF as defined below, or
a fluorinated aryl group ArF substituted on the aromatic ring with at least two groups selected from fluorine, a xe2x80x94CF(R9R10) group as defined above or a different ArF group, or
a fluorinated vinyl group VF substituted on at least two positions of the double bond with groups selected from fluorine, a xe2x80x94CF(R9R10) group or an ArF group as defined above;
the R8 group is hydrogen, xe2x80x94OH, xe2x80x94SH, or, together with said R5 group, it forms a carbonyl oxygen; and xe2x80x9cmxe2x80x9d can have the values of 0 or 1;
(B) an organometallic compound having the following formula (II):
Mxe2x80x2RnX(pxe2x88x92n)xe2x80x83xe2x80x83(II)
wherein: Mxe2x80x2 is a metal of group 2 or 13 of the periodic table of elements, preferably Mg or Al, more preferably Al, each R is independently a hydrocarbyl, preferably alkyl, group having from 1 to 10 carbon atoms,
each X is a halogen atom, preferably chlorine or bromine,
xe2x80x9cpxe2x80x9d is the valence of Mxe2x80x2 and is equal to 2 for group 2 and 3 for group 13,
xe2x80x9cnxe2x80x9d is a decimal number ranging from 1 to p, preferably p.
A second object of the present invention relates to a catalytic composition active in the (co)polymerization of xcex1-olefins comprising the following components in contact with each other:
the above organometallic composition; and
a metallocene complex of a metal of group 4 of the periodic table, comprising at least one cyclopentadienyl anion optionally substituted, pentahapto(xcex75-)co-ordinated to said metal.
This complex preferably has the following formula (III): 
wherein:
M represents a metal of group 4, specifically Ti, Zr or Hf;
each RA independently represents a group of an anionic nature bound to the metal M, different from cyclopentadienyl or substituted cyclopentadienyl;
xe2x80x9cwxe2x80x9d is an Index which can have integer values 1 or 2 depending on whether the valence of M is 3 or 4;
A represents an anionic ligand having from 5 to 30 carbon atoms, comprising an xcex75-cyclopentadienyl ring coordinated to the metal M;
RB, regardless of the nature of the other substituents, can have any of the meanings previously specified for the ligand A and for the group RA, and can also be connected with said group A by means of a divalent organic group having from 1 to 15 carbon atoms, to form a so-called xe2x80x9cbridgedxe2x80x9d metallocene complex.
Other possible objects of the present invention will appear evident from the following description and examples.
The term xe2x80x9c(co)polymerization of xcex1-olefinsxe2x80x9d as used hereafter in the text and claims, refers to both the homopolymerization and copolymerization of xcex1-olefins with each other or with another ethylenically unsaturated polymerizable compound.
According to the present invention, the above fluorinated organic compound having formula (I) is characterized by the presence in the molecule of a di-unsaturated cycle having 5 or 6 carbon atoms, i.e. a cyclopentadienyl ring or a 1,2,4,6-cyclohexadienyl ring, depending on whether the value of xe2x80x9cmxe2x80x9d in formula (I) is 0 or 1 respectively. Compounds having formula (I) with xe2x80x9cmxe2x80x9d=0 are preferred, however, owing to their greater activating capacity in polymerization processes of xcex1-olefins.
Each of the groups from R1 to R7 which form the substituents of this di-unsaturated cycle, can, when taken singly, be hydrogen, fluorine or an aliphatic or aromatic, monovalent hydrocarbyl group, optionally fluorinated. Typical but non-limiting meanings of the groups R1-R7 are: hydrogen, fluorine, methyl, trifluoromethyl, ethyl, pentafluoroethyl, 2,2,2-trifluoroethyl, 1,1-difluoroethyl, heptafluoroisopropyl, 1,1-difluorohexyl, perfluorocyclo-hexyl, pentafluorophenyl, ortho-, meta- and para-nona-fluorodiphenyl, 2,4,6-trifluorophenyl, 2,3,5-trifluorophenyl, 1,1-difluorobenzyl, heptafluorobenzyl, pentafluorophenylmethyl, 2,6-bis(trifluoromethyl)phenyl, 2,6-difluoro-4-trifluoromethylphenyl, etc. Fluoro, trifluo-romethyl, pentafluorophenyl, ortho- meta- or para-bis(trifluoro-methyl)phenyl groups are preferred as fluorinated groups owing to their high activating activity and the commercial availability of the precursors of compounds having formula (I) substituted with these groups.
When two or more R1-R7 groups are joined to each other to form cyclic structures comprising two atoms of the di-unsaturated cycle having formula (I), these Ri groups (i=1-7) are formally divalent and can be saturated or unsaturated to form saturated, unsaturated or aromatic rings, condensed with the first di-unsaturated cycle, preferably having from 5 to 8 carbon atoms, more preferably aromatic rings with 6 atoms. In this way compounds having formula (I) consisting of condensed di- or poly-cyclic structures are formed.
According to a preferred aspect of the present invention, the two groups R1 and R2, and optionally also the two groups R3 and R4 in the compound having formula (I) with xe2x80x9cmxe2x80x9d equal to 0, consist of fluorinated vinyl groups as defined above, which are bound to each other on the second unsaturated carbon so as to form one, or optionally two aromatic rings condensed with said di-unsaturated ring. In this way indenes or fluorenes (or the corresponding hydroxy- or thio-derivatives with R8 equal to xe2x80x94OH or xe2x80x94SH respectively) substituted on each aromatic ring with at least two groups selected from fluorine, fluorinated alkyl or fluorinated aryl, are respectively formed, in accordance with the requisites of the compounds having formula (I).
Among these polycyclic compounds, fluorenes are particularly preferred, and especially fluorenes having from 6 to 8 fluorine atoms, however arranged on the two aromatic cycles, as well as the corresponding hydroxy- and thio-derivatives.
According to a particular embodiment, component (A) of the organometallic composition of the present invention consists of a compound having formula (I) wherein the two groups R5 and R8 jointly represent a carbonyl oxygen atom. Cylcopentadienones and cyclohexadienones substituted on the ring with fluorine or fluorinated groups according to what is specified above, are therefore included in the scope of formula (I).
The compound having formula (I) preferably comprises from 5 to 50 carbon atoms and from 5 to 25 fluorine atoms. More preferably, this compound is a cyclopentadiene compound (xe2x80x9cmxe2x80x9d=0) having from 9 to 40 carbon atoms and from 9 to 25 fluorine atoms.
For example, compounds having formula (I) with xe2x80x9cmxe2x80x9d=1 are perfluoro-3-hydroxycyclohexa-1,4 diene, 1,2,3,4,5,6,6-heptafluorocyclohexa-1,4-diene, 1,2,4,5-tetrakis(pentaflu-orophenyl)cyclohexa-1,4-diene, 1,2,4,5-tetrakis(trifluoro-methyl)cyclohexa-1,4-diene, 1,2,4,5-tetrakis(pentafluoro-phenyl)-3-hydroxycyclohexa-1,4-diene, 9,10-dihydroperflu-oroanthracene, 9-hydroxy-9,10-dihydroperfluoroanthracene, 10,10-H,H-perfluoro-9-phenyl-9,10-dihydroanthracene, 10,10-H,H-9-hydroxyperfluoro-9-phenyl-9,10-dihydroanthracene.
Typical examples of fluorinated compounds having formula (I) with xe2x80x9cmxe2x80x9d=0 are fluorinated cyclopentadienes with at least three fluorine atoms on the ring, or, cyclopentadienes substituted with trifluoromethyl groups. Also included in the scope of formula (I) are derivatives of cyclopentadiene condensed with one or two extensively fluorinated aromatic rings, such as hexafluoro indene or octafluoro-fluorene. Other examples of compounds having formula (I) are indenes and fluorenes hydrogenated on the aromatic rings such as 4,4,7,7-tetrafluoro-4,5,6,7-tetrahydroindenes substituted with at least two fluorine atoms or two pentafluorophenyl groups on the cyclopentadienyl ring, and 1,1,4,4,5,5,8,8-octafluoro-1,2,3,4,5,6,7,8-octahydrofluorenes and the corresponding compounds substituted with a pentafluorophenyl group in position 9. In addition to these fluorinated hydrocarbon compounds, the corresponding hydroxy- and thio-derivatives substituted with an xe2x80x94OH or xe2x80x94SH group on the saturated position of the cyclopentadienyl ring, are typical examples of compounds included in formula (I)
According to a preferred embodiment of the present invention, in the compounds having formula (I) xe2x80x9cmxe2x80x9d is equal to 0 and R5 is selected from fluorine, pentafluorophenyl, nonafluorodiphenyl, bis(trifluoromethyl)phenyl and tris(trifluoromethyl)phenyl.
According to another embodiment of the present invention, 1,2,3,4,5,6,7,8-octafluorofluorenes wherein R6 is hydrogen or hydroxy and R5 is fluorine, trifluoromethyl, pentafluorophenyl or bis(trifluoromethyl)phenyl, are preferred as compounds having formula (I).
Further, specific and non-limiting examples of said compounds having formula (I) are: 1,2,4-tris-(pentafluorophenyl)cyclopentadiene, 1,2,3-tris-(pentafluorophen-yl)cyclopentadiene, 1,2,3,4-tetrakis(pentafluorophenyl)-cyclopentadiene, 1,2,3,4,5,6,7,8-octafluorofluorene, 1,2,3,4,5,6,7,8-octafluoro-9-hydoxy-9-(2,4-bis-trifluoro-methyl-phenyl)fluorene, 1,2,3,4,5,6,7,8-octafluoro-9-(2,4-bis-trifluoromethylphenyl)fluorene, 1,2,3,4,5,6,7,8-octa-fluoro-9-hydroxy-9-(3,5-bis-trifluoromethylphenyl)fluorene, 1,2,3,4,5,6,7,8-octafluoro-9-(pentafluorophenyl)fluorene, 1,2,3,4,5,6,7,8-octafluoro-9-hydroxy-9-(pentafluorophenyl)-fluorene, 1,2,3,4,5,6,7,8-octafluoro-9-hydroxy-9-(nonaflu-orodiphenyl)fluorene, 1,2,3,4,5,6,7,8-octafluorofluoren-9-one.
Mixtures of these cyclic compounds having formula (I) are equally suitable as component (A) of the organometallic compositions of the present invention.
Some of the compounds included in formula (I) are known in literature and their synthetic methods are described. For example pentafluorocyclopentadiene, octafluorofluorene, octafluoro-9-hydroxyfluorene, 9-penta-fluorophenyloctafluorofluorene, 2,3,4,5-tetrakis(trifluoromethyl)-1-hydroxycyclopentadiene, 1,2,3,4,5-pentakis-(trifluoromethyl)-cyclopentadiene, 1,4-bis(pentafluorophe-nyl)cyclopentadiene, 10,10-H,H-perfluoro-9-phenyl-9,10-di-hydroanthracene. As far as the Applicant knows, the use of these compounds and others having formula (I) which are not known, in the formation of an activating organometallic composition such as that object of the present invention, has never been disclosed or suggested.
In particular, the fluorinated cyclopentadiene compounds having formula (I) and having the following formula (IV) are new and form a further object of the present invention: 
wherein:
R5 and R6 have the same meaning defined for formula (I);
(y) is an integer from 1 to 4;
(z) is an integer from 1 to 4;
the groups R11 and R12 are independently substituents of hydrogen atoms of the respective aromatic ring in one or more of the four positions available, and are selected from fluorine or a fluorinated or non-fluorinated, aliphatic or aromatic hydrocarbyl group, having from 1 to 20 carbon atoms, optionally joined to a different R11 or R12 hydrocarbyl group, respectively, to form another cycle,
on the condition that at least 3, preferably at least 4, of the groups R5, R11 and R12 are independently selected from the group consisting of:
fluorine, or a fluorinated alkyl group having the formula xe2x80x94CF(R9R10) wherein each R9 or R10 group can have any of the above meanings of Ri groups and at least one of these is fluorine, or fluorinated alkyl at least in position 1, or a fluorinated aryl ArF as defined below, or a fluorinated vinyl group VF as defined below, or
a fluorinated aryl ArF substituted on the aromatic ring with at least two groups selected from fluorine, a xe2x80x94CF(R9R10) group as defined above or a different ArF group, or
a fluorinated vinyl group VF substituted on at least two positions of the double bond with groups selected from fluorine, a xe2x80x94CF(R9R10) group or an ArF group as defined above;
and in addition, R5 is different from H and, if R8 is H, R5 is different from pentafluorophenyl.
In a preferred embodiment, in the compounds having formula (IV), all the eight R11 and R12 are equal to each other and are trifluoromethyl or, even more preferably fluorine.
The above compounds having formula (I), even if new, can generally be obtained by adopting for the purpose the usual synthetic methods of organic chemistry, using the specific precursors and known reactions which the average expert in the field is capable of identifying on the basis of the structure of the desired compound. Examples of specific processes are described by R. Filler et al., in the publication xe2x80x9cJournal of Organic Chemistryxe2x80x9d, vol. 45 (1980); page 1290; by Vlasov V. M. et al. in the publication reviewed in xe2x80x9cChemical Abstractxe2x80x9d vol. 90 (1979), Nr.90:86522q; by Mark J. B. et al. in xe2x80x9cJournal of the American Chemical Societyxe2x80x9d, vol. 113 (1991), pages 2209-2222; by P. a. Deck et al. in xe2x80x9cOrganometallicsxe2x80x9d vol. 15 (1996), pages 5287-5291; by V. M. Vlasov in xe2x80x9cJournal of Fluorine Chemistryxe2x80x9d vol. 9 (1977), pages 321-325.
According to a particular process set up by the Applicant, octafluorene-9-hydroxy fluorenes substituted in position 9 with an alkyl or fluorinated aryl group can be obtained starting from perfluorofluorenone by the reaction with an equivalent quantity (about 1/1 in moles) of a lithium derivative having the formula R5Li (with R5 alkyl or fluorinated aryl having from 1 to 20 carbon atoms, preferably trifluoromethyl, pentafluoroethyl, pentafluorophenyl and bis(trifluoromethylphenyl), in a solution of a hydrocarbon solvent, preferably at temperatures ranging from xe2x88x9250 to +20xc2x0 C., followed by hydrolysis.
The corresponding octafluorofluorenes can be obtained from the hydroxy derivatives by the bromination reaction of the hydroxyl group with a suitable brominating agent such as PBr3, optionally followed by reduction by means of zinc or another reducing agent of the bromide group, to give the corresponding fluorinated hydrocarbon. In the specific case that xe2x80x9cyxe2x80x9d and xe2x80x9czxe2x80x9d are both 4, R11 and R12 are F and R5 in formula (IV) is 3,5-bis(trifluoromethyl)phenyl, it is not necessary to have any reduction step according to this preparative process.
Component (B) of the activating organometallic composition of the present invention consists, in its most general sense, of an alkyl compound of a metal of groups 2 or 13 of the periodic table, preferably Mg or Al, more preferably Al. This compound can also contain halogen atoms, especially chlorine, as well as the alkyl part. Non-limiting examples of these compounds are: Grignard reagents such as methylmagnesium chloride, ethylmagnesium chloride, octylmagnesium chloride and phenylmagnesium chloride; magnesium dialkyls such as magnesium diethyl, magnesium dibutyl, etc; aluminum alkyls and aluminum alkyl halides such as aluminum triethyl, aluminum tri-isobutyl, aluminum tri n-hexyl, aluminum tri-n-octyl, aluminum isoprenyl, aluminum diethylchloride, aluminum dibutylchloride, aluminumethyl sesquichloride, aluminum di-iso-butyl chloride and aluminum di-n-octyl chloride, aluminum triisoprenyl or their mixtures. Many of these organometallic compounds are known in the art and some are commercially available.
Aluminum alkyls which are particularly suitable as component (B) are aluminum trialkyls in which xe2x80x9cnxe2x80x9d in formula (II) is 3 and the three alkyl groups are equal to each other and have from 2 to 6 carbon atoms, such as aluminum triethyl, aluminum tributyl, aluminum tri-n-hexyl, aluminum triisobutyl or mixtures of these.
These aluminum alkyls are commercial products or can in any case be obtained by means.of the known preparative methods in organometallic chemistry.
In the activating organometallic composition of the present invention, the two components (A) and (B) are preferably present in molar ratios (B)/(A) ranging from 0.1 to 100. It has been found that the use of molar ratios (B)/(A) greater than 100 does not give any particular advantage to the catalytic system but is inconvenient as it increases the total quantity of aluminum which remains in the olefinic polymer at the end of the polymerization. Particularly preferred molar ratios (B)/(A) range from 1.0 to 10.
With reference to the quantity of component (B) effectively used for the preparation of the catalytic systems of the present invention, it should be pointed out that this can vary considerably in relation to various parameters associated with the subsequent use of the activating composition of the present invention. In particular, as can be seen hereunder, aluminum and magnesium alkyls having formula (II), especially aluminum trialkyls, can be used to a varying degree also for favouring the activation of the metallocene complex having formula (III), when the RA groups are different from alkyl or aryl, or, according to what is already known in the art (for example in xe2x80x9cJournal of Polymer Science, part Axe2x80x9d, vol. 32 (1994), pages 2387-2393), as xe2x80x9cscavengerxe2x80x9d to guarantee the removal or deactivation of poisoning impurities of the catalytic system possibly present in the reactor or polymerization solvent and monomers themselves. The portions of component (B) used in the different preparation phases of the catalyst and polymerization process contribute to determining the total quantity of metal of group 2 or 13, especially aluminum or magnesium, contained in the olefinic polymer obtained at the end of the polymerization, and represent a critical parameter, which as a rule should be as low as possible to give the polymer itself the desired dielectric properties for insulating applications and to avoid food contamination.
In addition, as will be described in more detail further on, in the formation of the catalytic composition of the present invention (activating organometallic composition+metallocene complex), it is possible both to pre-activate a chlorinated metallocene complex, for example with an aluminum alkyl, before contact with the actual activating composition itself, and to contemporaneously put the three compounds having formula (I), (II) and (III) respectively, in contact with each other in the suitable proportions. In this case, component (B) having formula (II) can be conveniently dosed in a greater quantity if the metallocene complex is chlorinated, in a lower quantity if the metallocene complex is alkylated.
With reference to the present invention, the quantities of said component (B) as a ratio of component (A), specified in the present description and claims, do not comprise the metal alkyl having formula (II), usually an aluminum trialkyl, optionally used as xe2x80x9cscavengerxe2x80x9d, which is normally introduced into the final preparation phase of the polymerization reactor, with concentrations ranging from 0.5 to 1 mmoles/l with respect to the volume of the polymerization mixture.
The activating organometallic composition according to the present invention is preferably prepared in a suitable hydrocarbon solvent, in an inert atmosphere, normally nitrogen or argon, by contact with components (A) and (B) in the desired proportions. The reaction between the two components occurs rapidly within a wide temperature range. The two components (A) and (B) can also be put in contact with each other in the presence of a metallocene complex having formula (III) in order to obtain the formation of a catalytic composition according to the present invention, in a single step.
The metallocene complex having formula (III) which forms component (ii) of the catalytic composition of the present invention can comprise both a single cyclopentadienyl ligand A, and two cyclopentadienyl ligands when R8 has this meaning.
In any case, the non-cyclopentadienyl RA and RB groups are preferably selected from hydride, halide, more preferably chloride or bromide, a hydrocarbyl or halogenated hydrocarbyl radical having from 1 to 30, preferably from 1 to 10, carbon atoms, different from cyclopentadienyl, a phosphonate, sulfonate or carbonate group, an alkoxy, carboxy or aryloxy group having from 1 to 20, preferably from 1 to 10, carbon atoms, an amide group, an organic group having from 1 to 20, preferably from 1 to 10, carbon atoms, bound to the metal M with an amide nitrogen atom, an organic group having from 1 to 20, preferably from 1 to 10, carbon atoms, bound to the metal M with a silicon atom.
Complexes having formula (III) wherein RB is different from cyclopentadiene are known in the art as monocyclopentadienyl complexes. A particular group of these complexes is that of the so-called xe2x80x9cconstrained metallocenesxe2x80x9d, in which the RB group, preferably an alkyl, alkylsilyl or alkylamide group, is bridge-bound with the single cyclopentadienyl group of the complex. These complexes are described for example in published patent applications EP-A 420,436, EP-A 418,044, EP-A 416,815.
Complexes of metals of group 4 comprising two cyclopentadienyl ligands, which are suitable as component (ii) in accordance with the present invention, are for example those represented by the following formula (V): 
wherein:
M represents a metal selected from titanium, zirconium or hafnium;
each Axe2x80x2 or Axe2x80x3 independently represents an organic group containing an xcex75-cyclopentadienyl ring of an anionic nature, coordinated to the metal M;
each Rxe2x80x2 or Rxe2x80x3 independently represents a group of an anionic nature "sgr"-bound to the metal M, preferably selected from hydride, halide, a C1-C20 alkyl or alkylaryl group, a C3-C20 alkylsilyl group, a C5-C20 cycloalkyl group, a C6-C20 aryl or arylalkyl group, a C1-C20 alkoxyl or thioalkoxyl group, a C2-C20 carboxylate or carbamate group, a C2-C20 dialkylamide group and a C4-C20 alkylsilylamide group.
According to the present invention, in particular, the groups Rxe2x80x2 and Rxe2x80x3 having formula (V) each independently represent a group of an anionic nature "sgr"-bound to the metal M. Typical examples of Rxe2x80x2 and Rxe2x80x3 are hydride, halide, preferably chloride or bromide, a linear or branched alkyl group such as methyl, ethyl, butyl, isopropyl, isoamyl, octyl, decyl, benzyl, an alkylsilyl group such as, for example, trimethylsilyl, triethylsilyl or tributylsilyl, a cycloalkyl group such as cyclopentyl, cyclohexyl, 4-methylcyclohexyl, an aryl group such as phenyl or toluyl, an alkoxyl or thioalkoxyl group such as methoxyl, ethoxyl, iso- or sec-butoxyl, ethylsulfide, a carboxylate group such as acetate, trifluoroacetate, propionate, butyrate, pivalate, stearate, benzoate, or again, a dialkylamide group such as diethylamide, dibutylamide, or alkylsilyl-amide group such as bis (trimethylsilyl)amide or ethyltrimethylsilylamide. The two groups Rxe2x80x2 and Rxe2x80x3 can also be chemically bound to each other and form a cycle having from 4 to 7 atoms different from hydrogen, also comprising the metal M. Typical examples of this aspect are divalent anionic groups such as the trimethylene or tetramethylene group, or the ethylenedioxy group. Rxe2x80x2 and Rxe2x80x3 groups which are particularly preferred for their accessibility and the easy preparation of the complexes comprising them, are chloride, methyl and ethyl.
According to the present invention, each group of an anionic nature A in formula (III) and Axe2x80x2 or Axe2x80x3 in formula (V), contains an xcex75-cyclopentadienyl ring coordinated to the metal M, which formally derives from a molecule of cyclopentadiene, substituted or non-substituted, by the extraction of an H+ ion. The molecular structure and typical electronic and coordinative configuration of metallocene complexes of titanium, zirconium or hafnium generally comprising two xcex75-cyclopentadienyl groups, is widely described in literature and is known to experts in the field.
In the more general form of the present invention, a divalent organic group, preferably containing from 1 to 20 carbon atoms, and optionally also one or more heteroatoms selected from silicon, germanium and halogens, can be bound to any of the carbon atoms of the cyclopentadienyl ring of groups Axe2x80x2 and Axe2x80x3 having formula (V) respectively (provided a bond valence is available).
Preferred Axe2x80x2 and Axe2x80x3 groups are the known cyclopentadienyl, indenyl or fluorenyl groups and their homologous products, wherein one or more carbon atoms of the molecular skeleton (included or not included in the cyclopentadienyl ring), are substituted with a radical selected from the group consisting of halogen, preferably chlorine or bromine, a linear or branched alkyl group having from 1 to 10 carbon atoms, optionally halogenated, such as methyl, trifluoromethyl, ethyl, butyl, isopropyl, isoamyl, octyl, decyl, benzyl, an alkylsilyl group such as, for example, trimethylsilyl, triethylsilyl or tributylsilyl, a cycloalkyl group such as cyclopentyl, cyclohexyl, 4-methylcyclohexyl, an aryl group having from 6 to 10 carbon atoms, optionally halogenated, such as phenyl, pentafluorophenyl or toluyl, an alkoxyl or thioalkoxyl group such as methoxyl, ethoxyl, iso- or sec-butoxyl, ethylsulfide, or again, a dialkylamide group, such as diethylamide, dibutylamide, or alkylsilyl-amide group such as bis(trimethylsilyl)amide or ethyltrimethylsilylamide. These Axe2x80x2 or Axe2x80x3 groups can also comprise several condensed aromatic rings, as in the case, for example, of 4,5-benzoindenyl. Particularly preferred Axe2x80x2 or Axe2x80x3 groups are cyclopentadienyl, indenyl, 4,5,6,7-tetra-hydroindenyl, fluorenyl, azulenyl and the corresponding methyl substituted groups.
Typical examples of complexes having formula (III) and/or (V) suitable for the purposes of the present invention are the compounds listed below, which however in no way limit the overall scope of the present invention.
(xcex75-C5H5)2TiCl2; [Me2Si(xcex75-C5Me4)(Nbut)]TiCl2;
xcex75-C5H5)2TiClMe; [1,2-en(xcex75-Ind)2]TiMe2;
(xcex75-C5H5)2TiCl3; (xcex75-C5Me5)TiCl2;
(xcex75-C5Me5)3TiCl; [1,2-en(xcex75-Ind)2]TiCl2;
(xcex75-C5H5)Ti(OCOMe)3; (xcex75-C5H5)2Ti(OCOPh)2;
[(xcex75-(3,5-CF3)2Bz)C5H4]2TiCl2; (xcex75-Ind)Ti(OCOMe)3;
(xcex75-C5Me5)Ti(OCOMe)3; [o-Xen-(xcex75-(THInd)2]TiCl2;
(xcex75-Ind)Ti(OCOCF3)2; [xcex75-(4-CF3Bz)C5H4]2TiCl2;
[xcex75-1,3-(CF3)2C5H3]Ti(OCOMe)2; (xcex75-C5H5)Ti(OCOCF3)2;
[1,2-en(xcex75-1-(4-CF3Bz)Ind)2]TiMe2; (xcex75-C5H5)Ti(OCOPh)3;
[Pri(xcex75-C5H5)(xcex75-Flu)]TiCl2; o-Bzn[1-(3-Me-xcex75-Ind)]2TiCl2;
o-Bzn-[1-(4,7-Me2)-xcex75-Ind]2TiBz2; [1.2-en(xcex75-Ind)2]ZrCl2;
o-Bzn-[1-(xcex75-THInd)2]TiCl2; [Ph2Si(xcex75-Ind)2]ZrCl2;
(xcex75-THInd)2ZrCl2; (xcex75-C5H5)2ZrCl2;
o-Bzn-[1-(4,7-Me2)-xcex75-Ind]2]TiBr2; (xcex75-Ind)Zr(NMe2)3;
[Pri(xcex75-C5H5)(xcex75-Flu)]ZrCl2; (xcex75-C5H5)2ZrCl(NMe2);
(xcex75-C5Me5)2ZrMe2; [1,2-en(xcex75-THInd)2]ZrCl2;
(xcex75-Ind)2Zr(NMe2)2; [Pri(xcex75-C5H5)(xcex75-Flu)]ZrCl2;
(xcex75-C5H5)2ZrCl(NMe2); [Me2Si(xcex75-Ind)2]HfCl2;
(xcex75-C5Me5)2ZrCl3; o-Bzn-[1-(4,7-(Me)2Ind)]2ZrCl2;
[o-Xen(xcex75-Ind)2]ZrCl2; (xcex75-C5Me5)Zr(OCOPh)3;
(xcex75-C5Me5)2ZrBz2; [1,2-en(xcex75-1-(2,4-(CF3)2Bz)Ind)2]ZrCl2;
[xcex75-(2,4-(CF3)2Bz)C5H4]2ZrCl2; [Me2Si(CH2-xcex75-C5H4)2]ZrCl2;
[o-Xen-(xcex75-C5H5)2]ZrCl2; (xcex75-THInd)2Zr(OCOCF3)2;
[o-Xen-(xcex75-THInd)2]ZrCl2; [o-Xen-(xcex75-THInd)2]ZrBz2;
[xcex75-(2,4-(CF3)2Bz)C5H4]2ZrCl(NMe2); [o-Xen(xcex75-C5H5)2]ZrMe2;
[o-Xen-(xcex75-C5H5)(xcex75-Flu)]ZrCl2; [xcex75-(4-Fxe2x80x94Ph)C5H4]2ZrCl2;
(xcex75-C5Me5)2ZrCl2; [Me2Si(CH2)2-(xcex75-Phxe2x80x94C5H3)2]ZrCl2;
o-Bzn[1-(5,6-(Me)2Ind)]2ZrCl2; [1,2-en(xcex75-THInd)2]ZrMe2;
o-Bzn-[1-(4,7-diphenyl)-xcex75-Ind]2ZrMe2; o-Bzn-(Flu)2HfCl;
o-Bzn[1-(-xcex75-THInd)2]ZrCl2; o-Bzn-[xcex75-C5Me4]2ZrCl2;
o-Bzn-[1(3-Me)-xcex75-Ind]2HfCl2; [Me2Si(xcex75-C5H4)2]HfCl2;
o-Bzn[1-xcex75-Ind)2Zr(OCO-n-C3H7)2; [Me2Si(xcex75-(1-Ind)2]HfCl2;
[Me2Si(xcex75-THInd)2]HfCl2; o-Bzn-[1-xcex75-(3-Me)Ind]2HfCl2;
The following abbreviations are used in the above formulae: Me=methyl, Et=ethyl, But=tert-butyl, Bz=benzyl, Pri=2,2-isopropylidene, Ind=indenyl, THInd=4,5,6,7-tetrahydro-indenyl, Flu=fluorenyl, 1,2-en=1,2-ethylidene, Ph2Si=diphenylsilylene, Me2Si=dimethylsilylene, o-Xen=ortho-xylylene, o-Bzn=ortho-benzylidene.
The catalytic composition according to the present invention comprises, and is obtained, by contact of the above components (i) and (ii). The selection of the metallocene component (ii) can be made each time by experts in the field on the basis of optimization criteria and industrial design, with reference to the specific characteristics of the metallocene complexes in relation to the various polymerization process parameters to be obtained.
Also included in the scope of the present invention are those catalytic compositions comprising two or more complexes having formula (III) or (V) mixed with each other. Catalytic compositions of the present invention based on mixtures of metallocene complexes having different catalytic behaviour can, for example, be advantageously used in polymerization, when a wider molecular weight distribution of the polyolefins thus produced, is desired.
When the metallocene complex having formula (III) does not comprise sufficiently reactive RA groups, such as for example alkyl or aryl, it is preferable, according to the present invention, to add to the catalytic composition object thereof, a sufficient quantity of organometallic compound having formula (II) capable of also acting as alkylating agent of said complex having formula (III). The compound having formula (II), more preferably an aluminum alkyl, can be added as a separate portion to the metallocene complex to form component (ii) of the catalytic composition, in a ratio Mxe2x80x2/M ranging from 1 to 10, preferably from 3 to 10, using a different portion for the formation of the activating organometallic composition (i), according to what is described above.
Alternatively, the whole compound having formula (II), also comprising the alkylating portion of the metallocene complex, can be put in contact with the fluorinated compound having formula (I) or with the metallocene complex having formula (III) and the product thus obtained is subsequently reacted with the missing component to form the catalytic composition of the present invention.
According to another aspect of the present invention, in order to produce solid components for the formation of polymerization catalysts of olefins, for example for use in polymerization in gas phase, the above complexes can also be supported on inert solids, preferably consisting of oxides of Si and/or Al, such as, for example, silica, alumina or silicoaluminates, but if necessary also of a polymeric nature, such as certain known polystyrenes functionalized for the purpose. The known supporting techniques can be used for the supporting of these catalysts, normally comprising contact, in a suitable inert liquid medium, between the carrier, optionally activated by heating to temperatures of over 200xc2x0 C., and one or both of components (i) and (ii) of the catalyst of the present invention. It is not necessary, for the purposes of the present invention, for both components to be supported, as only the complex having formula (III), or the activating composition which forms component (i), can be present on the surface of the carrier. In the latter case, the component which is missing on the surface is subsequently put in contact with the supported component, at the moment when the catalyst active for polymerization is to be formed.
Also included in the scope of the present invention are complexes, and the catalytic compositions based thereon, which have been supported on a solid by means of the functionalization of the latter and formation of a covalent bond between the solid and a metallocene complex included in the previous formula (III).
As well as the two components (i) and (ii), one or more additives or components can be optionally added to the catalytic composition of the present invention, according to what is known in normal practice of the polymerization of olefins, to obtain a catalytic system suitable for satisfying specific requisites in the field. The catalytic systems thus obtained should be considered as being included in the scope of the present invention. Additives or components which can be included in the preparation and/or formulation of the catalytic composition of the present invention are inert solvents, such as, for example, aliphatic and/or aromatic hydrocarbons, weakly coordinated additives selected, for example, from non-polymerizable olefins or particular fluorinated ethers, halogenating agents such as silicon halides, halogenated hydrocarbons, preferably chlorinated, etc., and again all other possible components normally used in the art for the preparation of traditional homogeneous catalysts of the metallocene type for the (co)polymerization of xcex1-olefins.
Components (i) and (ii) form the catalytic composition of the present invention by contact with each other, preferably in an inert diluent and at a temperature ranging from room temperature to the temperature selected for the polymerization which can also be, in certain processes, 150xc2x0 C. or higher, and for times varying from 10 seconds to 1 hour, more preferably from 1 to 30 minutes. Inert diluents suitable for the purpose are, for example, aliphatic and aromatic hydrocarbons liquid at room temperature.
The relative quantities between the two components of the present catalytic composition are selected so that the molar ratio (A)/(M), wherein (M) are the moles of metallocene complex having formula (III) and (A) the moles of fluorinated compound having formula (I), ranges from 0.5 to 50, preferably from 1 to 10. For ratio values higher than 50 there are no significant variations in the results obtained in polymerization processes.
It has been systematically observed that the catalytic composition in accordance with the present invention has a characteristic form of the ultraviolet spectrum, with a peak at much higher wave lengths, normally of at least 50 nm, with respect to the characteristic peak observed in the ultraviolet spectra of typical ionic metallocene catalysts obtained using the known activators based on tetrakis(pentafluorophenyl)boranes combined with the same metallocene complex.
FIGS. 1 and 2 of the present patent application indicate, for illustrative purposes, the ultraviolet spectra (A absorbance of various catalytic compositions obtained by contact and reaction at room temperature, in toluene as solvent, of the following components: